People need to step back from the brink of violence, Northern Ireland’s chief constable has said, amid rising tensions over disruption to Irish Sea trade from the rest of the UK after Brexit

Simon Byrne warned of a “febrile” atmosphere after 26 graffiti incidents were detected across the country, and officials carrying out customs checks at ports in Belfast and Larne withdrew following the threats.

Police said they have changed their operational tempo and will be accelerating development of intelligence.

Mr Byrne told the Policing Board in Belfast: “It is now time for wise words and calm heads.

“We need to work together to look at a route map to normality because that seems to be the opportunity before us, to step back from the brink in terms of community tension.”

Physical inspections on goods entering Northern Ireland from Great Britain, which are required under the Northern Ireland Protocol, have been suspended at ports amid intimidation of staff.

Police have insisted there is no evidence that loyalist paramilitaries are involved in the campaign, instead blaming disgruntled individuals and small groups.

Boris Johnson has warned he is ready to override elements of the Brexit divorce settlement relating to Northern Ireland to prevent a trade barrier developing in the Irish Sea.

In the Commons on Wednesday, DUP MP Ian Paisley told the Prime Minister the protocol has “betrayed” his constituents, making them “feel like foreigners in our country”.

European Commission vice-president Maros Sefcovic is due to travel to the UK for talks next week amid a deepening row between London and Brussels.

It comes amid growing concern that measures in the Withdrawal Agreement intended to keep open the land border with the Republic are disrupting trade between Northern Ireland and the rest of the UK.

The UK has requested an extension of grace periods of light touch regulation to allow the smooth flow of some trade.

Stormont First Minister Arlene Foster says the protocol should be replaced, but Dublin is focused on easing problems with the post-Brexit trade deal which have caused disruption at Irish Sea ports.

Irish Foreign Affairs Minister Simon Coveney said: “We need to be truthful with everybody – the protocol is not going to be scrapped.”

He said ministers want to be helpful and flexibilities are possible but the problems are a consequence of the UK’s Brexit negotiating stance.

Mr Coveney told the BBC’s Radio Ulster: “There is not going to be very dramatic change.”

The fraught situation was further exacerbated last week when the European Commission briefly used Article 16 of the protocol to close the border to exports of coronavirus vaccine from the Republic.

Mr Coveney said it is unrealistic to expect the protocol to be scrapped.

Mrs Foster told the BBC: “He is completely tone deaf to the concerns of unionism and he claimed to support the Belfast Agreement but the balance in the Belfast Agreement does not seem to matter.

“Just carry on regardless of the fact that there is not one unionist politician in Northern Ireland that supports the protocol, but what about it, we will just continue on.”

The DUP is pursing a series of political moves aimed at undermining the protocol, including a boycott on engagement with the Irish government on issues related to its operation and a vow to oppose any protocol-related legislation at the Assembly.

The party has also launched a parliamentary petition with the aim of getting the 100,000 signatures required for the matter to be consider for Westminster debate.

By 3pm on Thursday, within hours of it going live, the petition has attracted more than 20,000 signatures.